This invention relates to a carburetor for multiple kinds of fuels and more particularly to a multiple fuel system for an internal combustion engine offering improved cold starting operation.
Recently it has been proposed to operate motor vehicles on fuels other than what is commonly characterized as gasoline. For example, it has been proposed to operate vehicles on either alcohol or a mixture of alcohol and gasoline characterized as "gasohol." There are certain advantages to the use of such fuels. However, under cold starting conditions particularly at low temperatures such as temperatures lower than 15.degree. C., the alcohol and alcohol containing fuels may present certain difficulties in connection with starting due to the difficulties in igniting these fuels at such temperatures. Therefore, it has been proposed to provide an auxiliary fuel system for such engines that incorporate pure gasoline or other petroleum based fuels for cold starting. Once the engine has started and runs only briefly through the use of these starting fuels, it is possible to switch over the running of the engine on to the normal fuel. When this is done, however, the flow of starting fuel should be ceased. Failure to do so will cause rapid depletion of the starting fuel, which is normally supplied from a tank or reservoir having a much smaller capacity than a main reservoir. Failure to do so will, of course, make it difficult or impossible to restart the engine when it is again called and the ambient temperature is below 15.degree. C.
It is, therefore, a principal object of this invention to provide an improved multi-fuel system for an internal combustion engine.
It is another object of this invention to provide a multi-fuel system for an internal combustion engine wherein the flow of starting fuel is automatically discontinued once the cold starting operation has been completed.
In certain types of multi-fuel systems for internal combustion engines the carburetor or other charge forming device is provided with two separate fuel bowls and associated float-operated needle valves for maintaining the necessary fuel head in the system. One of these fuel bowls and associated float-operated needle valve assemblies controls the running fuel mixture. The other controls the starting mixture. As is well known, the fuel level in the float bowl varies during running conditions due to the inherent inability of the float-operated valve to stabilize its position. This presents no difficulty in connection with normal running of the engine since the opening of the float-operated valve will be compensated for by the consumption of fuel during normal running. In conjunction with the starting circuit, however, fluctuations will cause starting fuel to be consumed by the engine due to the inherent variations in the float position. With the previously proposed devices, the starting fuel flow is controlled between the float chamber and the point of introduction between this chamber and the induction system. Thus, even though the valve controlling the communication of starting fluid with the induction passage may be closed, excess starting fuel may be introduced into the induction passage or spilled from the venting arrangement during normal running, even though cold starting enrichment of this different fuel has been discontinued.
It is another object of this invention to provide an improved control arrangement for controlling the communication of starting fuel with the charge forming device during situations when cold starting enrichment using this other fuel is not required.
As has been noted in the foregoing description, multi-fuel engines require cold starting enrichment and the substitution of more ignitable fuels under certain low temperature conditions. In conjunction with such multi-fuel engines, it may be desirable to provide cold starting or cold running enrichment during intermediate temperatures which enrichment does not require the substitution of fuels. For instance, if the engine is operated on gasohol, or fuel mixtures which consist of a combination of gasoline and alcohol as aforedescribed, there are certain which which it is not necessary to substitute another fuel for starting. Nevertheless, it may be necessary to provide a enriched fuel-air mixture so as to facilitate starting and cold running during these intermediate temprature conditions. In the same regard, it may be necessary to provide a different starting fuel when the temperature falls below the aforedescribed intermediate range.
It is, therefore, a further object of this invention to provide an improved fuel feed arrangement for multi-fuel engines wherein different starting mixtures will be provided at different ambient temperatures.
It is yet a further object of this invention to provide a starting arrangement for a multi-fuel engine wherein enrichment of the fuel-air mixture based upon the normal running fuel is provided in certain temperature ranges and an enriched mixture of a different type of fuel is provided at other, lower temperatures.